There is some very intriguing information from the literature suggesting that if vitamin B12 does not readily enter cells, the synthesis of immunoglobulins is impaired. Therefore, we have proposed a series of studies to measure the release of immunoglobulins by both established lines of cultured lymphocytes and cultured peripheral cells. The dependence of these lymphocytes upon vitamin B12, folate, and transcobalamin II will be evaluated. These same factors will be correlated with immunoglobulin synthesis.